The present application claims priority upon Japanese Patent Application No. 2001-348654 filed on Nov. 14, 2001, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a tennis racket in which a frame and a shaft are formed from fiber-reinforced synthetic resin (FRP), and the shaft is inserted into a grip for connection thereto.
2. Description of the Related Art
In FRP-made tennis rackets, a shaft and a grip of the racket are integrally formed as a hollow body. Such FRP-made tennis rackets are widely adopted as rackets provided with lightweightness, flexibility and a desired strength. However, tennis rackets need to have a weight of more than a certain extent in order to obtain a desired stroke speed. Thus, lightweightness is not the only requirement for a tennis racket. Further, when flexibility is increased, not only does stroke control become difficult, but also, the damping ratio of vibration after stroking will be decreased. Thus, rigidity to some extent is necessary. On the other hand, if rigidity is increased, the shock transmissibility to the grip will be increased, and thus, problems such as tennis elbows will arise. Therefore, rackets with a good balance of flexibility and rigidity are desired.
Tennis rackets made from FRP only are superior in lightweightness and flexibility, but lack rigidity. Thus, various attempts have been made to pursue the optimal balance of flexibility and rigidity by attaching metal members/components onto a tennis racket.
One example of such an attempt is disclosed in Japanese Patent No. 3 085 261. Here, a structure is proposed in which a metal component is attached to surround a portion of the FRP-made shaft or the FRP-made frame.
Such a metal component can partially increase the rigidity of the shaft or the frame. However, it is not possible to substantially decrease the vibration transmitted to the grip, and attachment of the metal component to certain locations of a tennis racket resulted in significant increase in vibration.
The present invention has been contrived in view of the above-mentioned problems, and an objective of the present invention is to provide an FRP-made tennis racket improved in both shock transmissibility to the grip and in vibration-damping ratio by ensuring flexibility while increasing rigidity of the shaft.
In order to achieve the above-mentioned objective and other objectives, one aspect of the present invention provides a tennis racket comprising: a frame; a shaft connected to the frame at one end thereof; a grip into which the shaft is inserted at the other end thereof; and a pair of lightweight metal pieces attached to the shaft. Here, the frame and the shaft is formed from fiber-reinforced synthetic resin, and the pair of lightweight metal pieces has a U-shaped section and extends from inside the grip at a connecting portion with the shaft and along both sides of the shaft.